(1) Technical Field
The present invention is related to a valve system for implantation into a vessel and, more particularly, to a monolithic in situ forming prosthetic valve that is suitable for replacement of a defective valve or a diseased human valve, and methods for delivery thereof.
(2) Background
A variety of valve prostheses, in particular cardiac valve prostheses, have been developed for implantation into the human body. Previously, the large diameter and bulky structure of common prosthetic valves required implementation via open heart surgeries. During the past few years, percutaneous heart valve (PHV) replacement and repair has emerged as an additional therapy to potentially avoid the re-operation in young patients with congenital heart disease or severely sick patients. The challenge for this technology is to develop a collapsible and durable PHV that can be delivered through a reasonably small diameter lumen catheter, non-interfering with the normal anatomy, and being competent without significant valve stenosis.
One such collapsed valve is disclosed in U.S. Pat. No. 5,411,552 to Andersen et al. (the '552 patent), the entire contents of which are incorporated herein by reference. The '552 patent describes a fully formed valve delivered in a collapsed state and expanded in place via the use a balloon. The diameter of the fully formed valve is reduced to the point where it may be delivered in a percutaneous manner and expanded in situ. The device is placed at the desired location by a balloon that is used to expand the stent and the valve. While collapsible and expandable, a device according to the '552 patent is still undesirably large because it includes a pre-formed valve. For example, the device requires 20+French size delivery catheters to deliver the fully formed valve to the target site.
Another fully formed valve which is deliverable via a catheter is disclosed in U.S. Pat. No. 6,582,462 to Andersen et al. (the '462 patent), the entire contents of which are incorporated herein by reference. The '462 patent discloses a fully formed valve prosthesis comprising a collapsible elastic valve mounted on an elastic stent. The commissural points of the elastic collapsible valve are mounted on the cylindrical surface of the elastic stent. A catheter technique permits delivery of the fully formed valve to the target area without the need for surgical intervention in the body. Once at the target site, the collapsed and fully-formed valve and elastic stent are expanded. Once again, the '426 patent describes a fully formed valve. Thus, a disadvantage to this design is the relatively large size of the compressed radial diameter of the fully formed valve when delivered to the target area.
Similarly, U.S. Pat. No. 6,168,614 to Andersen et al. (the '614 patent), the entire contents of which are incorporated herein by reference, discloses a method for endovascularly delivering a fully formed valve through a blood vessel. The '614 patent discloses a variety of steps by which a fully formed tissue valve is attached with a support and delivered to a target site in a collapsed sate. Once in place and expanded, the valve is configured to permit blood flow in one direction and prevent blood flow in an opposite direction. The tissue valve and the support structure are secured to a desired valve location where the support structure and fully formed valve are expanded. As was the case above, a disadvantage to this design is the relatively large size of the compressed radial diameter of the fully formed valve when delivered to the target area.
Another example is U.S. Pat. No. 6,530,952 to Vesely (the '952 patent), the entire contents of which are incorporated herein by reference. The '952 patent discloses a cardiovascular valve system including a permanent base unit that is affixed to the patient using conventional sutures or staples, and a collapsible valve having a collapsible frame that mates with the permanent base unit, and supports valve leaflets. An installed collapsible frame may be re-collapsed and disengaged from the permanent housing whereas a new collapsible valve is then installed, to resume the function of the prosthesis. As was the case above, a drawback to the device of the '952 patent is that, although collapsed, the valve is pre-formed and therefore includes a relatively large, radial diameter.
Yet another example is U.S. Pat. No. 6,569,196 to Vesely (the '196 patent), the entire contents of which are incorporated herein by reference. The '196 patent discloses a system for minimally invasive insertion of a bioprosthetic heart valve. The system includes a collapsible tissue-based valve system, a catheter-based valve delivery system, a surgical platform and a device tracking and visualization system. The collapsible valve system includes a permanent outer frame that is affixed to the patient using conventional sutures or staples and a collapsible valve having a collapsible inner frame that mates with the outer frame. Once again, a drawback to the '196 patent is that it discloses a pre-formed valve.
Another example is U.S. Pat. No. 7,011,681, to Vesely (the '181 patent), the entire contents of which are incorporated herein by reference. The '181 patent discloses cardiovascular valve system including a permanent base unit that is affixed to the patient using conventional sutures or staples, and a collapsible valve having a collapsible frame that mates with the permanent base unit, and supports valve leaflets. An installed collapsible frame may be re-collapsed and disengaged from the permanent housing. A new collapsible valve is then installed, to resume the function of the prosthesis. Although collapsible, the valve is pre-formed which results in a relatively large radial diameter.
Another example is U.S. Patent Publication No. 2006/0135964, by Vesely (the '964 publication), the entire contents of which are incorporated herein by reference. The '964 publication discloses a cardiovascular valve system including a permanent base unit that is affixed to the patient using conventional sutures or staples, and a collapsible valve having a collapsible frame that mates with the permanent base unit, and supports valve leaflets. An installed collapsible frame may be re-collapsed and disengaged from the permanent housing. A new collapsible valve is then installed, to resume the function of the prosthesis. Once again, the collapsible valve is pre-formed.
Finally, U.S. Patent Publication No. 2006/0136052, by Vesely (the '052 publication), the entire contents of which are incorporated herein by reference, discloses cardiovascular valve assembly comprising a base member that is affixed to a patient using conventional sutures or staples, and a replaceable valve member including a valve frame that supports a plurality of valve leaflets. The valve member mates with the base member, and can be detached from the base member for convenient replacement. As was the case with the references above, the valve is pre-formed and therefore results in a relatively large radial diameter.
Each of the prior art stent valve designs has certain disadvantages. The prior art valve prosthesis generally consists of a support structure with a fully formed tissue valve connected to it. The support structure is typically delivered in a collapsed shape intraluminally and secured to a desired valve location with the support structure in an expanded shape. However, because the valves are delivered in a fully formed, collapsed state, the support structures tend to compressively impinge a portion of the leaflets of the tissue valve at the structure struts when the support structure is expanded by an inflatable balloon. The impinged leaflets tend to deteriorate and calcify, thereby decreasing the life of the valves. Additionally, because they are delivered in a fully formed state, the valves posses a radial diameter that, in some cases, is undesirable.
Thus, a continuing need exists for a deployable, in situ forming valve which has a minimal profile and which does not compressively impinge a portion of the leaflets of the tissue valve upon delivery, thereby decreasing the risk of deterioration and/or calcification.